go-tour: add -content flag
go-tour: add -content flag

Fixes issue 11

R=golang-dev, adg, r
CC=golang-dev
https://codereview.appspot.com/12038049

Committer: Andrew Gerrand <395a7d33bec8475c9b83b7d440f141bcbd994aa5@golang.org>

minux/go-tour-zh,minux/go-tour-zh,Go-zh/tour-old,Go-zh/tour-old